This invention relates in general to the field of impact attenuation devices, and more particularly to an energy absorbing system which may be used to reduce the severity of a collision between a moving motor vehicle and a stationary hazard adjacent to a roadway.
Various impact attenuation devices and energy absorbing systems have been used to prevent or reduce damage resulting from a collision between a moving motor vehicle and a fixed roadside hazard or obstacle. Examples of prior impact attenuation devices and energy absorbing systems include crash cushions or crash barriers with various structures and containers having crushable elements. Other crash barriers rely on inertia forces generated when material such as sand is accelerated during an impact to absorb energy.
Some of these devices and systems have been developed for use at narrow roadside hazards or obstacles such as at the end of a median barrier, end of a barrier extending along the edge of a roadway, large sign posts adjacent to a roadway, and bridge pillars or center piers. Such impact attenuation devices and energy absorbing systems are installed in an effort to minimize the extent of personal injury as well as damage to an impacting vehicle and any structure or equipment associated with the roadside hazard.
Examples of general purpose impact attenuation devices are shown in U.S. Pat. No. 5,011,326 entitled Narrow Stationary Impact Attenuation System; U.S. Pat. No. 4,352,484 entitled Shear Action and Compression Energy Absorber; U.S. Pat. No. 4,645,375 entitled Stationary Impact Attenuation System; and U.S. Pat. No. 3,944,187 entitled Roadway Impact Attenuator. Examples of specialized stationary energy absorbing systems are shown in U.S. Pat. No. 4,928,928 entitled Guardrail Extruder Terminal and U.S. Pat. No. 5,078,366 entitled Guardrail Extruder Terminal. Each of the preceding patents is incorporated by reference for all purposes in the present application.
Examples of impact attenuation devices and energy absorbing systems appropriate for use on a slow moving or stopped highway service vehicle are shown in U.S. Pat. No. 5,248,129 entitled Energy Absorbing Roadside Crash Barrier; U.S. Pat. No. 5,199,755 entitled Vehicle Impact Attenuating Device; U.S. Pat. No. 4,711,481 entitled Vehicle Impact Attenuating Device; U.S. Pat. No. 4,008,915 entitled Impact Barrier for Vehicles.
Recommended procedures for evaluating performance of various types of highway safety devices including crash cushions is presented in National Cooperative Highway Research Program (NCHRP) Report 350. A crash cushion is generally defined as a device designed to safely stop an impacting vehicle within a relatively short distance. NCHRP Report 350 further classifies crash cushions as either xe2x80x9credirectivexe2x80x9d or xe2x80x9cnonredirectivexe2x80x9d. A redirective crash cushion is designed to contain and redirect a vehicle impacting downstream from a nose or end of the crash cushion facing oncoming traffic extending from a roadside hazard. Nonredirective crash cushions are designed to contain and capture a vehicle impacting downstream from the nose of the crash cushion. Redirective crash cushions are further classified as either xe2x80x9cgatingxe2x80x9d or xe2x80x9cnongatingxe2x80x9d devices. A gating crash cushion is one designed to allow controlled penetration of a vehicle during impact between the nose of the crash cushion and the beginning of length of need (LON) of the crash cushion. A nongating crash cushion is designed to have redirection capabilities along its entire length.
In accordance with teachings of the present invention, disadvantages and problems associated with the previous impact attenuation devices and energy absorbing systems have been substantially reduced or eliminated. One aspect of the present invention includes providing a crash barrier or crash cushion which may be installed adjacent to a fixed roadside hazard or obstacle to protect occupants of a vehicle from collision with the roadside hazard. The crash cushion preferably includes a cutter plate and a series of rip plates or energy absorbing elements which cooperate with each other to absorb energy from a vehicle impacting one end of the crash-cushion opposite from the fixed roadside hazard. The rip plates remain relatively fixed within the crash cushion while the cutter blade moves through the rip plates to absorb energy from the vehicle impact. The crash cushion also includes improved panels and associated panel support frames to redirect a vehicle impacting with either side of the crash cushion.
Another aspect of the present invention includes providing an energy absorbing system having a plurality of panel support frames and panels which may be installed between a road side hazard and oncoming traffic. The panel support frames and panels are slidably disposed relative to each other. As a result, when a vehicle collides with one end of the energy absorbing system facing oncoming traffic, the panel support frames and panels will telescope or collapse relative to each other to cushion the impact from the vehicle. The panel support frames, associated panels and other components of the energy absorbing system cooperate with each other to absorb kinetic energy from the vehicle and provide deceleration within acceptable limits to minimize injury to occupants within the vehicle. The panel support frames and panels also cooperate with other components of the energy absorbing system to direct vehicles away from the road side hazard and back onto the roadway following a collision with either side of the energy absorbing system.
Technical advantages of the present invention include providing a crash cushion which may be fabricated at relatively low cost using conventional materials and processes that are well known to the highway safety industry. The resulting crash cushion combines innovative structural and energy absorbing techniques that are highly predictable and reliable. Energy from vehicle impact is preferably absorbed by ripping, cutting or tearing one or more energy absorbing elements. The crash cushion may be easily reused following vehicle impact by replacing one or more energy absorbing elements. A wide variety of metal strips and metal plates may be satisfactorily used as energy absorbing elements depending upon the intended operating environment for the crash cushion. Also, the number of energy absorbing elements and their geometric configuration may be varied depending upon the intended application.
In accordance with another aspect of the present invention, a crash cushion is provided with multiple energy absorbing elements disposed adjacently to one end of a fixed roadside hazard facing oncoming traffic. The energy absorbing elements cooperate with each other to allow varying the amount of deceleration applied to a vehicle impacting one end of the crash cushion opposite from the fixed roadside hazard. For example, the crash cushion may include a first, relatively soft portion to absorb impact from small, lightweight vehicles, a middle portion with increased stiffness and a third or final portion with the greatest amount of stiffness to absorb impact from heavy, high speed vehicles.
Still another aspect of the present invention includes providing a crash cushion with multiple panels which are preferably nested with each other to minimize any problems associated with a xe2x80x9creverse anglexe2x80x9d impact between a vehicle and either side of the crash cushion. The panels and associated panel support frames preferably telescope with respect to each other in response to a vehicle impact at one end of the crash cushion opposite from the fixed roadside hazard. The number of panel support frames and associated panels may be selected in accordance with teachings of the present invention to optimize deceleration of an impacting vehicle while protecting occupants of the vehicle from injury due to excessive amounts of deceleration.
Further technical advantages of the present invention include providing relatively low cost crash cushions which meet the criteria of NCHRP Report 350 including Level 3 Requirements. A crash cushion having a cutter plate and energy absorbing elements incorporating teachings of the present invention may be satisfactorily used during harsh weather conditions and is not sensitive to cold or moisture. A cutter plate and energy absorbing elements incorporating teachings of the present invention can absorb large amounts of energy while safely stopping an impacting vehicle during a relatively short length of travel of the cutter plate through the energy absorbing elements.
The cutter plate and energy absorbing elements cooperate with each other and with panel support frames and associated panels to eliminate many of the problems associated with prior crash cushion designs. A crash cushion incorporating teachings of the present invention can satisfactorily dissipate kinetic energy of an impacting vehicle weighing 4,500 pounds at speeds of over sixty miles per hour (60 mph) with minimal damage (if any) to the roadside hazard and minimal debris (if any) from the crash cushion. A crash cushion incorporating teachings of the present invention provides highly predictable deceleration of an impacting vehicle to protect occupants of the vehicle.
In addition to eliminating problems associated with prior crash cushion designs, the present invention provides a crash cushion offering a higher level of protection to the motoring public with greater improved reliability and reduced costs. The resulting crash cushion provides appropriate deceleration or stopping force for a wide range of vehicle sizes and types including vehicles weighing between 820 kilograms and 2,000 kilograms.
A further aspect of the present invention includes a crash cushion having a sled assembly with a cutter plate attached thereto and multiple energy absorbing assemblies connected with each other by a series of cross ties or anchor plates. As a result of connecting the energy absorbing assemblies with each other, the crash cushion has a rigid frame construction which in cooperation with multiple panel supporting frames and associate panels will redirect vehicles during side impacts with the crash cushion.
For some applications each energy absorbing assembly includes two C-channels with the C shaped configurations facing each other and the C-channels extending generally horizontally in the direction of oncoming vehicle traffic during normal operation of the crash cushion. A gap of approximately one inch is provided between opposing flanges of the two C-channels. This gap may be covered by one or more metal plates or energy absorbing elements to form a closed box type structure. A cutter blade or ripper is preferably attached to the lower portion of a sled assembly at the end of the crash cushion facing oncoming traffic. During impact between a motor vehicle and the sled assembly, forces from the collision are transferred from the sled assembly to the energy absorbing assemblies by the cutter blade. As the sled assembly moves toward the fixed roadside hazard, the metal plates or energy absorbing elements which are attached on opposite sides of the C-channels are cut or ripped by the cutter blade. The energy of the impacting vehicle is dissipated and the impacting vehicle brought safely to rest by the force required to cut or rip the metal plates of the energy absorbing assemblies. Various combinations of metal plates and supporting beams may be used to form each energy absorbing assembly to provide appropriate stopping or deceleration for a wide range of vehicle types, weights and speeds of impact. Supporting beams having configurations other than C-channels may be satisfactorily used with the present invention.
Technical advantages of the present invention include providing a crash cushion which may be easily installed, operated and maintained. Easily replaceable parts allow quick, low cost repair after nuisance hits and side impacts. Elimination of easily crushed or easily bent materials further minimizes the effect of any damage from nuisance hits and/or side impacts with the crash cushion.